Examples

        <%= icon 'copyright-mark' %>
        %= icon 'sort-by-attributes-alt'

        <span class="glyphicon glyphicon-copyright-mark"></span>
        <span class="glyphicon glyphicon-sort-by-attributes-alt"></span>

        <%= icon 'copyright-mark' %>

        <span class="glyphicon glyphicon-copyright-mark"></span>

        %= icon 'sort-by-attributes-alt'

        <span class="glyphicon glyphicon-sort-by-attributes-alt"></span>